The present disclosure relates to an image forming apparatus including a process unit in which a drum unit supporting a photosensitive drum and a development unit supporting a developing device are attachably/detachably provided.
An image forming apparatus, such as a printer or a copying machine, may be configured so that a drum unit rotatably supporting a photosensitive drum, a development unit supporting a developing device and an intermediate transferring unit rotatably supporting an intermediate transferring belt are installed to a process frame.
In such an image forming apparatus, positioning parts positioned to each unit and the process frame mutually are formed. In a case where each unit is installed to the process frame from an upper side, a positioning boss is formed in each unit and a U-shaped gap engageable with the boss is formed in the process frame. When each unit is installed to the process frame, the boss is inserted into the U-shaped gap from the upper side, and then, each unit is positioned to the process frame.
However, in a case where positioning is composed of the boss and the U-shaped gap as mentioned above, if the image forming apparatus is shocked by tumbling or falling upside down, it is feared that the boss is detached from the U-shaped gap. In order to prevent the boss from being detached, an inlet of the U-shaped gap may be formed smaller than a diameter of the positioning boss and the boss may be lightly press-fitted to the U-shaped gap. But, in a case where such lightly press-fitting is required, attaching and detaching of each unit take time and labor. Moreover, in a case where a shock applied to the image forming apparatus is large, it is difficult to surely position the boss to the U-shaped gap.